Air battery is a battery comprising oxygen as a cathode active material and the battery takes in air from outside at a time of discharge. So, compared with other types of battery which include active materials of a cathode and an anode in it, it is possible to enlarge the ratio of the volume of the anode active material to the volume of the battery container. Accordingly, air battery, theoretically, has a larger dischargeable electric capacity; downsizing and weight saving of the battery can also be easily done. Moreover, since the oxidation power of oxygen to be used as a cathode active material is strong, the electromotive force of the battery is relatively high. Further, oxygen is an unlimited resource and a clean material, so the environmental burden of air battery is low. In this way, air battery has many advantages and therefore expected to be used as, for example, a battery for mobile phone, a battery for electric vehicle, a battery for hybrid car, and a battery for fuel cell vehicle.
As the conventionally proposed air batteries, the nonaqueous electrolyte-type air battery using metal lithium as an anode material and oxygen as an air electrode material is known.
In the nonaqueous electrolyte-type air battery, oxygen is reduced to be Li2O2 or Li2O at the air electrode during discharge reactions . These reactions can be shown as follows.2Li++O2+2e−—>Li2O2  (Formula 1)4Li++O2+4e−—>2Li2O  (Formula 2)
Here, Gibbs free energy ΔG of Li2O2 is −606.68 kJ/mol and Gibbs free energy ΔG of Li2O is −560.66 kJ/mol. When calculating the theoretical operating voltage by using these values and a formula: ΔG=−nFE, the theoretical operating voltage of Li2O2 is 3.1 V, and the theoretical operating voltage of Li2O is 2.9 V. However, the actual operating voltage of the conventional nonaqueous electrolyte-type lithium air battery is not more than 2.6 V. The reason is assumed that the overvoltage increases due to the large activation barrier required for oxygen reduction, as a result, the actual operating voltage is lower than the theoretical operating voltage. So, if the activation barrier required for oxygen reduction can be lowered, it is presumably possible to provide an air battery which shows an actual operating voltage equivalent to the theoretical one.
As an art relates to such a nonaqueous electrolyte-type lithium air battery, for example, Patent document 1 discloses a nonaqueous electrolyte-type lithium air battery which comprises: a cathode mainly containing a carbonaceous matter of which pore volume occupied by fine pores having a diameter of 1 nm or more is 1.0 mL/g or more; an anode containing an anode active material which absorbs and discharges lithium ions; and a nonaqueous electrolyte layer sandwiched between the cathode and the anode.